Self-aggregation and phase behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solution

Almgren, Mats; Brown, Wyn; Hvidt, Søren

doi:10.1007/bf00655668

Cited by 449 publications

(521 citation statements)

References 43 publications

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“…As the copolymer concentration is 1.20, 1.12 and 2.13 times the critical micellar concentration (cmc) for F68, F88 and F108, respectively, one expects a larger concentration of bigger aggregates in the case of F108. The behaviour of PEO-PPO-PEO copolymers in water has been well investigated [38][39][40][41][42][43][44][45][46][47] and, it is well-established that the values of the aggregation number are highly dependent on the copolymer molecular weight and this is similarly observed in our experiments (Table 2). In particular, the mean aggregation number hNi increases with the copolymer size and is very small for F68.…”

Section: Resultssupporting

confidence: 81%

Selectivity of cyclodextrins as a parameter to tune the formation of pseudorotaxanes and micelles supramolecular assemblies. A systematic SANS study

2011

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We studied the formation of polypseudorotaxanes formed with cyclodextrins (CDs) threading a copolymer chain that forms self-assembled structures in water. The size of the CD cavity was chosen such that it is block selective with respect to the formation of inclusion complexes and therefore in terms of altering the structure of the copolymer self-assemblies in a systematic fashion. Small angle neutron scattering (SANS) experiments provide a direct and clear picture of the shape and interactions of the copolymer micelles in the absence and the presence of various CDs. Moreover, the dissolution of copolymer micelles by CD addition was clearly described by a simple model which provides a tool for quantitative predictions. This study suggests the possibility of designing materials with tunable aggregation abilities in water, where the extent of aggregate formation is determined by the amount and type of added cyclodextrin.

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Section: Resultssupporting

confidence: 81%

Selectivity of cyclodextrins as a parameter to tune the formation of pseudorotaxanes and micelles supramolecular assemblies. A systematic SANS study

2011

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“…[30][31][32][33] The observation of coexistence is not surprising in itself, given that for a two-component system one expects coexistence regions along each phase boundary. However, for almost all the transitions examined here the coexistence window is very small (i.e., e1°C), whereas near the L/C 2 window in DEP the interval is as much as 40°C and ∆φ ≈ 0.1 wide.…”

Section: Discussionmentioning

confidence: 99%

Phase Behavior of a Block Copolymer in Solvents of Varying Selectivity

2000

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The effect of the thermodynamic selectivity of a solvent on the self-assembly of a styreneisoprene (SI) diblock copolymer with block molecular weights of 1.1 × 10 4 and 2.1 × 10 4 g/mol is investigated. We explore the phase behavior from the melt state to dilute solution in solvents that are of varying selectivities for the two blocks. Bis(2-ethylhexyl) phthalate (DOP) is a neutral good solvent for SI. Di-n-butyl phthalate (DBP) and diethyl phthalate (DEP) are good solvents for PS but marginal and poor, respectively, for PI. Tetradecane (C14) is utilized as a complementary solvent that is good for PI but poor for PS. Small-angle X-ray scattering (SAXS) and static birefringence are used to locate and identify order-order (OOT) and order-disorder transitions (ODT). Dynamic and static light scattering were used to characterize the dilute solution micellar behavior. The neat polymer forms the gyroid (G 1) morphology at low temperature, an OOT to hexagonal-packed cylinders (C1) occurs at 185°C, and the ODT is located at 238°C. Dilution with DOP decreases the OOT temperature in agreement with the dilution approximation, i.e., OOT ∼ φ -1 , but the ODT follows a stronger dependence of ODT ∼ φ -1.4 . The slightly selective solvent DBP stabilizes the ordered state relative to DOP. Rich lyotropic and thermotropic behavior is observed among regions of lamellae (L), inverted gyroid (G2), inverted hexagonal-packed cylinders (C2), and inverted body-centered-cubic spheres (S2 bcc ). Solutions in DEP display similar morphological behavior, along with significantly increased ODT temperatures. Because of the asymmetric block copolymer composition, the phase behavior in the isoprene-selective solvent C14 is markedly different, as only G1, C1, and S1 bcc phases are observed. The overall sequence of phases with dilution and/or heating is rationalized on the basis of diagonal trajectories across the phase map (temperature vs composition) for undiluted block copolymers: addition of a neutral solvent corresponds to increasing the temperature and thus a "vertical" trajectory, whereas the partitioning between microdomains of a selective solvent amounts to a "horizontal" trajectory to a renormalized block volume composition. However, a variety of novel features are observed in DEP: the formation of face-centered-cubic packed micelles, a reentrant thermotropic ODT, and a large window of L + C 2 coexistence. The dependence of the principal length scale, d*, on φ, T, and structure is also considered. The strongly temperature-dependent selectivity produces a crossover in the scaling of d* vs φ for the lamellar phase: the addition of a selective solvent increases d*, but as the solvent becomes neutral, d* decreases. This phenomenon is captured by selfconsistent mean-field calculations.

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“…[59] In general, Pluronics lead to formation of lamellar vesicles in water, with the hydrophobic PPO blocks shielded from the aqueous phase by hydrophilic PEO blocks protruding out from the vesicle wall on both sides. The size of the vesicles can be tuned upon addition of additives (e.g., surfactants) and/or polar organic solvents (e.g., ethanol).…”

Section: Polymer Aggregatesmentioning

confidence: 99%

Recent Progress on Silica Coating of Nanoparticles and Related Nanomaterials

2010

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In recent years, new strategies for silica coating of inorganic nanoparticles and organic nanomaterials, which differ from the classical methodologies, have emerged at the forefront of materials science. Silica as a coating material promises an unparalleled opportunity for enhancement of colloidal properties and functions by using core-shell rational designs and profiting from its synthetic versatility. This contribution provides a brief overview of recent progress in the synthesis of silica-coated nanomaterials and their significant impact in different areas such as spectroscopy, magnetism, catalysis, and biology.

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Self-aggregation and phase behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solution

Cited by 449 publications

References 43 publications

Selectivity of cyclodextrins as a parameter to tune the formation of pseudorotaxanes and micelles supramolecular assemblies. A systematic SANS study

Selectivity of cyclodextrins as a parameter to tune the formation of pseudorotaxanes and micelles supramolecular assemblies. A systematic SANS study

Phase Behavior of a Block Copolymer in Solvents of Varying Selectivity

Recent Progress on Silica Coating of Nanoparticles and Related Nanomaterials

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